Currently test/run uses wildcards to run all of the tests in a directory.
However, that wildcard list is filtered down by the "onlyfor" directives
in the test files... usually to a single file.

Therefore, just explicitly list the files we *really* want to run for this
test mode.  This makes it easier to see at the top level what tests will
be executed, and to change that list temporarily while debugging specific
failures.

This means the "onlyfor" directive no longer has any purpose, and we can
remove it.  "onlyfor" was also the only used of the $MODE variable, so we
can remove that too.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

A number of the testcases use options specific the OpenBSD version of
netcat.  That's available in Debian, but not easily available in Fedora.
Switch the pasta tests to using the nmap version of netcat (a.k.a. ncat).
This is easily available in both Debian and Fedora, and appears to be a
bit more modern and maintained as well.

ncat generally requires explicit listen addresses (which is good for
clarity anywhere).  Its default options appear to remove the need for the
-N and -q options.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[sbrivio: changed one ncat listening address to IPv6 loopback]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

A number of tests and examples use dhclient in both IPv4 and IPv6 modes.
We use "dhclient -6" for IPv6, but usually just "dhclient" for IPv4.  Add
an explicit "-4" argument to make it more clear and explicit.

In addition, when dhclient is run from within pasta it usually won't be
"real" root, and so will not have access to write the default global pid
file.  This results in a mostly harmless but irritating error:
    Can't create /var/run/dhclient.pid: Permission denied
We can avoid that by using the --no-pid flag to dhclient.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

ip(8)'s ability to take abbreviated arguments (e.g. "li sh" instead of
"link show") is very handy when using it interactively, but it doesn't make
for very readable scripts and examples when shown that way.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

'sleep' always needs an argument, this was meant to introduce
a 2 seconds delay.

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Build-time selection of AVX2 flags and routines is not practical for
distributions, but limiting AVX2 usage to checksum routines with
specific run-time detection doesn't allow for easy performance gains
from auto-vectorisation of batched packet handling routines.

For x86_64, build non-AVX2 and AVX2 binaries, and implement a simple
wrapper replacing the current executable with the AVX2 build if it's
available, and if AVX2 is supported by the current CPU.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

To reach (at least) a conceptually equivalent security level as
implemented by --enable-sandbox in slirp4netns, we need to create a
new mount namespace and pivot_root() into a new (empty) mountpoint, so
that passt and pasta can't access any filesystem resource after
initialisation.

While at it, also detach IPC, PID (only for passt, to prevent
vulnerabilities based on the knowledge of a target PID), and UTS
namespaces.

With this approach, if we apply the seccomp filters right after the
configuration step, the number of allowed syscalls grows further. To
prevent this, defer the application of seccomp policies after the
initialisation phase, before the main loop, that's where we expect bad
things to happen, potentially. This way, we get back to 22 allowed
syscalls for passt and 34 for pasta, on x86_64.

While at it, move #syscalls notes to specific code paths wherever it
conceptually makes sense.

We have to open all the file handles we'll ever need before
sandboxing:

- the packet capture file can only be opened once, drop instance
  numbers from the default path and use the (pre-sandbox) PID instead

- /proc/net/tcp{,v6} and /proc/net/udp{,v6}, for automatic detection
  of bound ports in pasta mode, are now opened only once, before
  sandboxing, and their handles are stored in the execution context

- the UNIX domain socket for passt is also bound only once, before
  sandboxing: to reject clients after the first one, instead of
  closing the listening socket, keep it open, accept and immediately
  discard new connection if we already have a valid one

Clarify the (unchanged) behaviour for --netns-only in the man page.

To actually make passt and pasta processes run in a separate PID
namespace, we need to unshare(CLONE_NEWPID) before forking to
background (if configured to do so). Introduce a small daemon()
implementation, __daemon(), that additionally saves the PID file
before forking. While running in foreground, the process itself can't
move to a new PID namespace (a process can't change the notion of its
own PID): mention that in the man page.

For some reason, fork() in a detached PID namespace causes SIGTERM
and SIGQUIT to be ignored, even if the handler is still reported as
SIG_DFL: add a signal handler that just exits.

We can now drop most of the pasta_child_handler() implementation,
that took care of terminating all processes running in the same
namespace, if pasta started a shell: the shell itself is now the
init process in that namespace, and all children will terminate
once the init process exits.

Issuing 'echo $$' in a detached PID namespace won't return the
actual namespace PID as seen from the init namespace: adapt
demo and test setup scripts to reflect that.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Debug information might be printed after a prompt is seen,
just wait those 3 seconds and be done with it.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>